Re: gEDA-user: sparkfun 4 layer boards

[John Griessen <john@xxxxxxxxxxxxxx>]

John Doty wrote:
> On Aug 23, 2008, at 12:48 PM, John Griessen wrote:
>>  120 deg F is plenty good, and the amount of near IR in
>> that temperature surface is
>> enough to see with a CCD I bet.
> 
> Nope. Quantum efficiency of silicon detectors drops like a rock just  
> beyond 1 µm wavelength: the radiation just goes right through without  
> interacting. Indeed, Si wafers make excellent entrance windows for  
> for thermal IR detectors.
> 
> A 350 K blackbody emits ~271 µW/mm^2 of thermal radiation, but only  
> ~4.4 fW/mm^2 of that is short of 1 µm.

Dang!  Thanks for educating me.

> On the other hand, a 350 K component is pretty easy to find with your  
> finger...

And to think I've forgotten that much since working for SBRC making 
detector related circuits!   Silicon having 1 µm cutoff window 
properties is a great memory aid.  Won't forget that relation now, thanks,

John Griessen


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